The invention relates to a method for separating gas mixtures formed above liquids, especially hydrocarbon gas mixtures, by using a separating device comprising a gas separation membrane, on the retentate side of which a mixture (retentate) diminished in one or more components and on the permeate side of which a mixture (permeate) enriched by one or more components can be generated, as well as to a device for performing this method.
It is known that, for example, upon filling of containers with liquids, gases, respectively, gas mixtures comprised of the components of the liquid are formed directly at the filling location. In the past, this gas, respectively, gas mixture, resulting from processes governed by natural laws, has been released in most situations into the surroundings in an uncontrolled manner, for example, during filling of gas tanks of motorized vehicles at gas stations directly into the air. The uncontrolled release of gas, respectively, gas mixtures during such transfer, respectively, refilling operations has two considerable disadvantages. On the one hand, a considerable amount of the liquid is released in a gaseous form into the surroundings, which results in a considerable economical disadvantage, and, on the other hand, the environment as well as the person performing the transfer, respectively, filling operation is exposed to considerable amounts of noxious gases.
For eliminating these considerable disadvantages it has been suggested among other things due to regulatory mandates, for example, for the filling of tanks of motorized vehicles, to provide the so-called pump nozzle, from which the fuel exits in order to be filled into the motorized vehicle, with a sealing sleeve that encloses the tank socket and parts of the nozzle whereby the transition of the tank socket to the nozzle is sealed relative to the surroundings. Via this sealing sleeve the gases formed during the filling operation are enclosed relative to the surroundings and returned into the tank. In this manner it is to be ensured that during filling of the tank of a motorized vehicle, which is applicable in the same manner in general to other containers to be filled, the gases respectively, gas mixtures formed during transfer, respectively, filling cannot exit from the tank but instead are recycled within a closed system. In this context, a filter which is, in general, provided within a tank vent of any liquid containing tank and is, for example, in the form of an active carbon filter designed to reduce the venting loss of such tanks, serves to absorb the gases that are formed within the tank, respectively, container of a motorized vehicle. The goal is to return the displaced gas volume from an operating liquid tank into a storage tank from which the liquid has been transferred into the operating liquid tank. This is also referred to by the term "gas shuttling". Gas shuttling is demanded by law in different countries and comprises the installation of a small active carbon container within motorized vehicles for reducing the venting losses as well as for gas shuttling at gas stations.
It is an object of the present invention to provide a method and a device of the aforementioned kind with which the last mentioned systems can be improved such that an even more effective return of gases, respectively, gas mixtures into the liquid container is possible whereby the method shall be performed with simple means and the device for performing the method should be cost-effective and essentially maintenance-free so that the method and/or the device can be used in large numbers, for example, at any suitable fuel pump or as a central unit of a gas station for motorized vehicles etc., so that thereby the environmental impact and the health risk to the person performing the refilling operation can be reduced to limits that are safe with respect to the environment and health.